/* ============================================
   CSS Variables & Theme System
   ============================================ */
:root {
    /* Light Theme */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-tertiary: #94a3b8;
    --border-color: #e2e8f0;
    --border-hover: #cbd5e1;
    
    /* Brand Colors */
    --primary: #6366f1;
    --primary-hover: #4f46e5;
    --primary-light: #e0e7ff;
    --success: #10b981;
    --warning: #f59e0b;
    --error: #ef4444;
    
    /* UI Elements */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    
    --transition: 200ms ease;
}

[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-tertiary: #64748b;
    --border-color: #334155;
    --border-hover: #475569;
    --primary-light: #312e81;
}

/* ============================================
   Base Styles
   ============================================ */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    transition: background var(--transition), color var(--transition);
}

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

input, select {
    font-family: inherit;
}

/* ============================================
   Header
   ============================================ */
.header {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    padding: 16px 24px;
    position: sticky;
    top: 0;
    z-index: 100;
    transition: background var(--transition), border-color var(--transition);
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-icon {
    font-size: 28px;
}

.logo h1 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
}

.theme-toggle {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 8px 12px;
    font-size: 20px;
    transition: all var(--transition);
}

.theme-toggle:hover {
    background: var(--bg-tertiary);
    border-color: var(--border-hover);
}

/* ============================================
   Main Content
   ============================================ */
.main-content {
    flex: 1;
    padding: 32px 24px;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

/* ============================================
   Upload Section
   ============================================ */
.upload-section {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 60vh;
}

.upload-container {
    text-align: center;
    max-width: 600px;
    width: 100%;
}

.upload-area {
    background: var(--bg-secondary);
    border: 2px dashed var(--border-color);
    border-radius: var(--radius-lg);
    padding: 48px 32px;
    cursor: pointer;
    transition: all var(--transition);
}

.upload-area:hover,
.upload-area.drag-over {
    border-color: var(--primary);
    background: var(--primary-light);
}

.upload-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
}

.upload-icon {
    font-size: 48px;
    margin-bottom: 8px;
}

.upload-content h2 {
    font-size: 1.5rem;
    color: var(--text-primary);
}

.upload-content p {
    color: var(--text-secondary);
}

.upload-hint {
    font-size: 0.875rem;
    color: var(--text-tertiary);
}

.supported-formats {
    margin-top: 24px;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.privacy-notice {
    margin-top: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    color: var(--text-secondary);
    font-size: 0.875rem;
    padding: 12px 16px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
}

.privacy-icon {
    font-size: 16px;
}

/* ============================================
   Processing Section
   ============================================ */
.processing-section {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 60vh;
}

.processing-container {
    text-align: center;
    max-width: 500px;
    width: 100%;
}

.processing-spinner {
    width: 60px;
    height: 60px;
    border: 4px solid var(--border-color);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 24px;
}

.processing-container h2 {
    font-size: 1.5rem;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.processing-container > p {
    color: var(--text-secondary);
    margin-bottom: 24px;
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-sm);
    overflow: hidden;
    margin-bottom: 8px;
}

.progress-fill {
    height: 100%;
    background: var(--primary);
    border-radius: var(--radius-sm);
    transition: width 300ms ease;
    width: 0%;
}

.progress-text {
    color: var(--text-tertiary);
    font-size: 0.875rem;
    margin-bottom: 24px;
}

/* ============================================
   Editor Section
   ============================================ */
.editor-section {
    animation: fadeIn 300ms ease;
}

.editor-container {
    display: grid;
    grid-template-columns: 1fr 350px;
    gap: 24px;
}

.image-display {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.image-wrapper {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
    background: 
        linear-gradient(45deg, var(--bg-tertiary) 25%, transparent 25%),
        linear-gradient(-45deg, var(--bg-tertiary) 25%, transparent 25%),
        linear-gradient(45deg, transparent 75%, var(--bg-tertiary) 75%),
        linear-gradient(-45deg, transparent 75%, var(--bg-tertiary) 75%);
    background-size: 20px 20px;
    background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
    min-height: 400px;
}

.comparison-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
    width: 100%;
    max-width: 100%;
}

.image-side {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
}

.image-side h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
}

.image-side canvas {
    max-width: 100%;
    max-height: 400px;
    object-fit: contain;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
}

.zoom-controls {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px;
    background: var(--bg-primary);
    border-top: 1px solid var(--border-color);
}

.zoom-btn {
    width: 36px;
    height: 36px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 18px;
    font-weight: bold;
    color: var(--text-primary);
    transition: all var(--transition);
}

.zoom-btn:hover {
    background: var(--bg-tertiary);
    border-color: var(--border-hover);
}

.zoom-level {
    min-width: 48px;
    text-align: center;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-primary);
}

/* ============================================
   Controls Panel
   ============================================ */
.controls-panel {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    display: flex;
    flex-direction: column;
    gap: 24px;
    max-height: calc(100vh - 200px);
    overflow-y: auto;
}

.action-buttons {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 20px;
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    font-weight: 500;
    transition: all var(--transition);
    text-decoration: none;
}

.btn-primary {
    background: var(--primary);
    color: white;
    border: 1px solid var(--primary);
}

.btn-primary:hover {
    background: var(--primary-hover);
    border-color: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background: var(--bg-primary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--bg-tertiary);
    border-color: var(--border-hover);
}

.btn-icon {
    font-size: 1.1em;
}

/* Tabs */
.options-tabs {
    display: flex;
    gap: 4px;
    background: var(--bg-primary);
    padding: 4px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
}

.tab-btn {
    flex: 1;
    padding: 10px 16px;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    transition: all var(--transition);
}

.tab-btn:hover {
    color: var(--text-primary);
    background: var(--bg-secondary);
}

.tab-btn.active {
    background: var(--primary);
    color: white;
}

/* Tab Content */
.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 200ms ease;
}

.tab-content h3 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 16px;
}

/* Form Elements */
.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.form-select,
.form-input {
    width: 100%;
    padding: 10px 12px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    color: var(--text-primary);
    transition: border-color var(--transition);
}

.form-select:focus,
.form-input:focus {
    outline: none;
    border-color: var(--primary);
}

.form-range {
    width: 100%;
    height: 6px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-sm);
    outline: none;
    -webkit-appearance: none;
}

.form-range::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 18px;
    height: 18px;
    background: var(--primary);
    border-radius: 50%;
    cursor: pointer;
}

.form-range::-moz-range-thumb {
    width: 18px;
    height: 18px;
    background: var(--primary);
    border-radius: 50%;
    cursor: pointer;
    border: none;
}

.form-color {
    width: 100%;
    height: 40px;
    padding: 4px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    cursor: pointer;
}

.help-text {
    font-size: 0.75rem;
    color: var(--text-tertiary);
    margin-top: 4px;
}

/* Color Options */
.color-options {
    display: flex;
    gap: 8px;
    align-items: center;
}

.color-btn {
    padding: 8px 16px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    color: var(--text-primary);
    transition: all var(--transition);
}

.color-btn:hover {
    background: var(--bg-tertiary);
}

.color-btn.active {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

.color-picker {
    width: 40px;
    height: 32px;
    padding: 0;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    cursor: pointer;
}

/* Background Type Grid */
.bg-type-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
}

.bg-type-btn {
    padding: 12px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    color: var(--text-primary);
    transition: all var(--transition);
}

.bg-type-btn:hover {
    background: var(--bg-tertiary);
}

.bg-type-btn.active {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

/* Gradient Grid */
.gradient-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
}

.gradient-btn {
    height: 48px;
    border-radius: var(--radius-md);
    border: 2px solid var(--border-color);
    cursor: pointer;
    transition: all var(--transition);
}

.gradient-btn:hover {
    border-color: var(--primary);
    transform: scale(1.05);
}

/* ============================================
   Footer
   ============================================ */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: 16px 24px;
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.875rem;
    transition: background var(--transition), border-color var(--transition);
}

/* ============================================
   Animations
   ============================================ */
@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 968px) {
    .editor-container {
        grid-template-columns: 1fr;
    }
    
    .controls-panel {
        max-height: none;
    }
    
    .comparison-container {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 640px) {
    .header-content {
        padding: 0 16px;
    }
    
    .main-content {
        padding: 24px 16px;
    }
    
    .upload-area {
        padding: 32px 20px;
    }
    
    .upload-content h2 {
        font-size: 1.25rem;
    }
    
    .action-buttons {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
    }
    
    .bg-type-grid {
        grid-template-columns: 1fr;
    }
}

/* ============================================
   Reduced Motion
   ============================================ */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}